Analysis of Fiber Orientation in the Wood-Polymer Composites (WPC) on Selected Examples

The fibers orientation in the polymer matrix is an important factor determining mechanical properties of products made of composites by means of an injection molding process. The fibers arrangement has an effect on shrinkage of the composite and the dimensional accuracy of molded piece. The knowledge of fiber orientation can determine the proper dimensions and design of the molding cavities and then correct some of physical and mechanical properties of the molded piece. The orientation of fillers depends on many factors, among which the important role play processing parameters including the injection speed. The aim of this study was to assess the orientation of the fibers in wood-polymer composite on the selected examples. The knowledge and proper use of micromechanical models allow to evaluate the fibers flow and their orientation in polymer matrix. The research was performed both for numerical simulations and experimental studies for results verification

The Optimization of PHBV-hemp Fiber Biocomposite Manufacturing Process on the Selected Example

In this work, a modern biocomposite on the base of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) matrix commonly known as PHBV was produced in the extrusion process, containing 30% by weight of hemp fibers. The use of the above-mentioned filler allowed to reduce the producing costs of the composite material compared to pure PHBV, improving, among others, some mechanical properties of products made of this biocomposite while maintaining full biodegradation. The obtained biocomposite can be successfully used for the production of injection molded products, but its processing properties are not yet fully known and consequently it is difficult to obtain the optimal performance properties of the products. As part of this study, the process of optimization of the production process of products from the PHBV-hemp fiber biocomposite was carried out on the example of samples intended for testing in the uniaxial tensile test. By using orthogonal planes, widely used in optimization process, the required number of injection molding tests was reduced. Input data values were determined by the factorial planning method that is commonly used in designing experiments. The calculations were carried out in the Minitab 18 software. Six controlling factors were used in the analyzes, each of which was subject to changes on three levels. When selecting the range of controlling factors, it was initially assumed that for all assumed levels of variability it must be possible to fill the mold cavity completely. The orthogonal plan of the L27 type was used in the research. For the purposes of the method, an orthogonal table was built containing 27 combinations of parameters subject to optimization. Optimization was undertaken for two main criteria: shrinkage of the ,,dog-bone” samples (primary and secondary volumetric shrinkage), mechanical properties (Young's modulus, tensile strength, elongation at break). By means of Taguchi method, a significant improvement of some product mechanical properties made of biocomposite was noted and the effective reduction of the processing shrinkage was observed